Testing is done inside a Docker container for maximum repeatability. We don't use Travis-CI or friends because we need to be able to kill our process dependencies (MongoDB, Redis, ...) on demand.
Therefore you need to install docker to run the tests. If you're not on an os that supports natively docker, don't forget to start up your VM and ssh into it.
$ make test
You can also open a shell inside the docker (just like you would enter in a virtualenv) with:
$ make docker
$ make ssh